a) Field of the Invention
In an ophthalmic microscope (e.g., a slit lamp), an illumination arrangement is used for generating changeable illumination fields, illumination colors and illumination intensities in and on the eye. The use of diffuse survey or broad-beam illumination, circular illumination fields with variable diameter, and sharply delimited light slits for generating an optical sectional image through transparent media of the eye is conventional. Formerly, exclusively mechanical/optical elements such as pinhole diaphragms and slit diaphragms, filter glasses, test targets or patterns, etc. were used to change the illumination field geometry.
b) Description of the Related Art
A typical ophthalmic microscope is described in Document No. 311214-7560.145 by Carl Zeiss.
All of the previously known methods and arrangements have faults.
Adjustment of the mechanical component groups is very complicated. The parallelism of the slit edges in the case of a very narrow slit is difficult to guarantee. Thermal expansion of mechanical structural component parts and shaking caused by transporting can necessitate readjustment. The reproducibility of settings for measurement purposes is limited. The arrangement of operating controls is predetermined to a great extent by the mechanical construction and ergonomic concerns cannot always be taken into account in an optimum manner.
The multiplicity of conceivable illumination field geometries is limited by the respective fixed slit diaphragms and pinhole diaphragms. In particular, the possibilities for displaying test patterns are very limited. The space requirement for the illumination device is correspondingly large due to the use of mechanically adjustable component groups for changing the illumination field geometry (drives, displacement elements, diaphragms).
In WO 96/04581, a DMD mirror is used for projection of vision tests.